Pathogenic Shigellae and Yersiniae are one ofthe leading causes of foodborne diseases. While these diseases can be theoretically treated with antibiotics, the high incidence of the multidrug-resistant strains means that development of new antimicrobial treatments is critical. Bacteria corrupt numerous biochemical pathways of the host and understanding of these mechanisms directly contributes to the novel target drug discovery as well as it facilitates research on the established drug targets. However, many important aspects ofthe bacteria-host protein interactions remain unknown. Deubiquitinating enzymes (DUBs) regulate ubiquitination, a reversible modification that controls protein function, stability and localization. Our long-term goal is to understand the functions of DUBs in bacterial infection in order to facilitate discovery of novel therapies and diagnostics. The overall objective in this proposal is to determine the functions of DUBs in the foodborne diseases caused by Shigella and Yersinia by using an integrated proteomics approach and functional studies. Our central hypothesis is that human DUBs, such as 0TUB1, and their associated protein networks are central to virulence in shigellosis and yersiniosis, and that DUB activity is regulated by bacteria and host, consequently determining the disease outcome. Assessment of DUB-associated protein networks and their role in pathogenesis is novel and innovative. We will use two very different enteropathogens to unveil conserved as well as strain-specific biological functions of the DUBs. The rationale for the proposed research is that once we know functions and downstream pathways of DUBs affected by these infections, we can quantify the relevance of DUBs to these diseases and apply this information to a rational drug design.